TCX file from BigRingVR won't import - "An error occurred during transfer

Hi,

I'm trying to import a TCX file from BigRingVR (indoor cycling app) into Garmin Connect and keep getting the error "An error occurred during transfer. Please try again."

Here's what I've tried:

• Importing the original file → same error
• Rebuilding the TCX from scratch with only 100 trackpoints (99 KB) → same error
• Converting to GPX → same error
• Converting to FIT → "file type not supported"
• Tapiriik → blocked by Garmin API

What's strange:

• Other TCX files from the same app (BigRingVR) import perfectly fine
• The problematic activity is a 1h22 cycling session from March 4, 2026
• No duplicate activity exists on that date in my account
• The file validates correctly as XML and imports fine on Strava

Has anyone encountered this issue with a specific activity being refused no matter what? Could Garmin be blocking imports based on activity duration, distance, or some other criteria?

Thanks